Image signal processing apparatus, image signal processing method, prediction coefficient generating apparatus, prediction coefficient generating method, and programs for causing computer to execute the methods

1. An image signal processing apparatus comprising: a block division unit that inputs an image signal encoded by orthogonal transformation and that divides the encoded image signal into second blocks different from first blocks encoded using the orthogonal transformation; an activity calculation unit that calculates an activity of each of the second blocks divided by the block division unit; a re-encoding unit that encodes the second blocks divided by the block division unit using the orthogonal transformation; a re-encoded difference calculation unit that calculates difference values between the second blocks re-encoded by the re-encoding unit and the first blocks encoded using the orthogonal transformation; a class determination unit that determines a class of each of the second blocks on the basis of a distribution of the difference value calculated by the re-encoded difference calculation unit and the activity calculated by the activity calculation unit; a prediction coefficient generating unit that generates a prediction coefficient corresponding to each of the classes determined by the class determination unit; a prediction tap construction unit that constructs a prediction tap for calculating a target pixel in each of the second blocks; and a predictive operation unit that operates the prediction tap constructed by the prediction tap construction unit and the prediction coefficient generated by the prediction coefficient generating unit to calculate a pixel value of each of the target pixels.

2. The image signal processing apparatus according to claim 1 , wherein the class determination unit includes: a first vector data conversion unit that generates vector data formed of the difference value calculated by the re-encoded difference calculation unit and the activity calculated by the activity calculation unit; a first class code storage unit that stores pieces of typical vector data, each of which represents the difference value calculated by the re-encoded difference calculation unit and the activity calculated by the activity calculation unit; and a first minimum value determination unit that determines typical vector data having a minimum norm to the vector data generated by the first vector data conversion unit from among the pieces of typical vector data stored in the first class code storage unit.

3. The image signal processing apparatus according to claim 1 , further comprising: an interblock difference calculation unit that calculates a difference value between predetermined pixels in the adjacent second blocks in regard to the plurality of second blocks divided by the block division unit, wherein the class determination unit determines a class of each of the second blocks on the basis of a distribution of the difference value calculated by the re-encoded difference calculation unit, the activity calculated by the activity calculation unit, and the difference value calculated by the interblock difference calculation unit.

4. The image signal processing apparatus according to claim 3 , wherein the class determination unit includes: a second vector data conversion unit that generates vector data formed of the difference value calculated by the re-encoded difference calculation unit, the activity calculated by the activity calculation unit and the difference value calculated by the interblock difference calculation unit; a second class code storage unit that stores pieces of typical vector data, each of which represents a distribution of the difference value calculated by the re-encoded difference calculation unit, the activity calculated by the activity calculation unit and the difference value calculated by the interblock difference calculation unit; and a second minimum value determination unit that determines typical vector data having a minimum norm to the vector data generated by the second vector data conversion unit from among the pieces of typical vector data stored in the second class code storage unit.

5. The image signal processing apparatus according to claim 4 , further comprising: a waveform class calculation unit that calculates a class on the basis of a characteristic amount of a waveform in a target pixel and pixels around the target pixel in each of the second blocks; and a class integration unit that integrates the class determined by the class determination unit with the class determined by the waveform class calculation unit to determine a class, wherein the prediction coefficient generating unit generates a prediction coefficient corresponding to the class determined by the class integration unit.

6. An image signal processing method comprising the steps of: dividing an image signal into first blocks and then encoding the image signal using orthogonal transformation; dividing the encoded image signal into second blocks different from the first blocks; calculating an activity of each of the divided second blocks; re-encoding the second blocks using the orthogonal transformation; calculating difference values between the re-encoded second blocks and the first blocks encoded using the orthogonal transformation; determining a class of each of the second blocks on the basis of a distribution of the calculated difference value and the activity; generating a prediction coefficient corresponding to the determined class; constructing a prediction tap for calculating a target pixel in each of the second blocks; and operating the constructed prediction tap and the prediction coefficient to calculate a pixel value of the target pixel.

7. A non-transitory computer program product having computer readable instructions stored thereon that when executed by a computer causes the computer to execute an image signal processing method comprising: dividing an image signal into first blocks and then encoding the image signal using orthogonal transformation; dividing the encoded image signal into second blocks different from the first blocks; calculating an activity of each of the divided second blocks; re-encoding the second blocks using the orthogonal transformation; calculating difference values between the re-encoded second blocks and the first blocks encoded using the orthogonal transformation; determining a class of each of the second blocks on the basis of a distribution of the calculated difference value and the activity; generating a prediction coefficient corresponding to the determined class; constructing a prediction tap for calculating a target pixel in each of the second blocks; and operating the constructed prediction tap and the prediction coefficient to calculate a pixel value of the target pixel.

8. A prediction coefficient generating apparatus comprising: an encoding unit that encodes an image signal divided into first blocks using orthogonal transformation; a decoding unit that decodes the image signal encoded by the encoding unit; a block division unit that inputs the image signal decoded using the orthogonal transformation and that divides the encoded image signal into second blocks different from the first blocks encoded using the orthogonal transformation; an activity calculation unit that calculates an activity of each of the second blocks divided by the block division unit; a re-encoding unit that encodes the second blocks divided by the block division unit using the orthogonal transformation; a re-encoded difference calculation unit that calculates difference values between the second blocks re-encoded by the re-encoding unit and the first blocks encoded using the orthogonal transformation; a class determination unit that determines a class of each of the second blocks on the basis of a distribution of the difference value calculated by the re-encoded difference calculation unit and the activity calculated by the activity calculation unit; a prediction tap construction unit that constructs a prediction tap for calculating a target pixel in each of the second blocks; and a prediction coefficient operation unit that, for each position of a target pixel of each second block in the class, calculates a prediction coefficient that minimizes a difference between a pixel value of the target pixel and a pixel value of the corresponding first block on the basis of the class determined by the class determination unit, the prediction tap constructed by the prediction tap construction unit and pixels of the image signal divided into that first block.

9. A prediction coefficient generating method comprising the steps of: dividing an image signal into first blocks and then encoding the image signal using orthogonal transformation; decoding the encoded image signal; inputting the image signal encoded using the orthogonal transformation and dividing the encoded image signal into second blocks different from the first blocks; calculating an activity of each of the divided second blocks; re-encoding the second blocks using the orthogonal transformation; calculating difference values between the re-encoded second blocks and the first blocks encoded using the orthogonal transformation; determining a class of each of the second blocks on the basis of a distribution of the calculated difference value and the activity; constructing a prediction tap for calculating a target pixel in each of the second blocks; for each position of the target pixel of each second block in the class, calculating a prediction coefficient that minimizes a difference between a pixel value of the target pixel and a pixel value of the corresponding first block on the basis of the class, the prediction tap and pixels of the image signal divided into that first block.

10. A non-transitory computer program product having computer readable instructions stored thereon that when executed by a computer causes the computer to execute a prediction coefficient generating method comprising: dividing an image signal into first blocks and then encoding the image signal using orthogonal transformation; decoding the encoded image signal; inputting the image signal encoded using the orthogonal transformation and dividing the encoded image signal into second blocks different from the first blocks; calculating an activity of each of the divided second blocks; re-encoding the second blocks using the orthogonal transformation; calculating difference values between the re-encoded second blocks and the first blocks encoded using the orthogonal transformation; determining a class of each of the second blocks on the basis of a distribution of the calculated difference value and the activity; constructing a prediction tap for calculating a target pixel in each of the second blocks; for each position of the target pixel of each second block in the class, calculating a prediction coefficient that minimizes a difference between a pixel value of the target pixel and a pixel value of the corresponding first block on the basis of the class, the prediction tap and pixels of the image signal divided into that first block.